Apparatus for drying leather



Nov. 22, 1955 J. KAHN ETAL APPARATUS FOR DRYING LEATHER Filed Feb. 26, 1952 INVENTORS Ju Z 710 K5, 2 1/ Mauricio Pie?" EmiZz'oZV. Zlfaoflznney ATTORNEYS tio'n times' as many skins can be processed as with the old United States Patent t 2,724,191 APPARATUS FOR DRYING LEATHER Julio Kahn', Mauriciolier, and Emilio N. MacKinney, 1 Mexico City, Mexico t t Applicatian February 26,1952, Serial No. 273,480

i l Claim. c1. 34--68) 'l his inven'tion relates to apparatus for drying leather ahdis especially applicable tothe drying of chrome tanned leather but is not limited thereto.

In the known and now generally used conventional proce's'sbf drying tanned leather, the skins having therein the fat liquonand after having been wrung and set out, are pas'ted toa carryingplate with a starch type or potato d rived paste the plates being of glass, and the thus treated are excessively dry. 1 r t The present process is an entirely new approach to and solution of the problem of drying tanned leather (herein referred toas skins) wherebynot only is a better prodnot obtained but also a very significant increase in producobtained} n it being estimatedtthat about thirty processyin the same amount of time.

" While our process hasbeenvfound to be exceptionally well suited"to treatmenthof chrome tanned leathers, it

caii also: be used for other leathers, such as for example will stand a suitable boil test or can withstand the temperatures involved in our process." In our process, the

leather being treated does not become hotor get burned, so'rnetimes referred to} in the trade as cooked. Instead,

thileather comes through at a very moderate temperature andtin a pliablewcondition andhas a nice feel to r the touch. 1 t,

lntour pro'cess, theleather skin, in this instance chrome tanned leather, as it normally comes out. of thetreating vatr and after being wrung and set out as is customary in the trade, the leather being at room temperature of usually, toSO degrees Fahrenheit, is pastedto a vertical supporting plate and the plate with the, leather thereon ist hen moved into a, first zone of a current of con stantlymoving heated air at a temperature ranging from 350to ,550 degreeslFahrenheita At the'same time as this sudden, application of high temperature heat, we subject the leather also to abombardment ofinfra-red rays,these rays and the heat being derived from an in direct flame from the burning of a gas. The supporting plate is preferably ofamaterial such as enameled metal, stainless steel,=or Monel metal, andhas a reflecting and conducting surface. The treatment in this first zone takes place for a period of from two to five minutes,

The plate with'the leatherathereon is then moved intoa second ,zone ,of 'a moving current of air having agtemw perature range ,Offl'OXIlj-ZQOIO 300 degrees Fahrenheit for a period of from 3 to 7 minutes. The time of treatment varies with the thickness of the leather being treated and the most desirable time is easily determined from observation of the treated leather.

We are unaware as to the specific scientific reason for the fact that the leather dried by our process is neither burned nor damaged but instead is dried in a fraction of the usual time and with better results. ,Our theory is that there is a colloidal dispersion throughout the leather, of the fat liquor particles in the leather, caused by'the sudden bombardment of infra-red rays in the high heat and the moving current of air, and that the fat liquor residue in the leather or the greasing materials, whichever one may prefer to call them, is driven outwardly away from the pasted surface to the outer surface of the leather or skin and is carried off by the currentof moving air, The result in the leather appears to be a deep drying effect and yet there is sufiicient moisture left to give the leather a proper texture and to avoid excessive drying with the bad results incident to such excessive removal of rnoisture. Our process is in effect a controlled removal of moisture or drying at high speed, a condition which has heretofore been unknown to the tanning and drying industry which to now has held to the belief that such leather would only be properly dried Without injury through the very slow processes heretofore known.

Thus, our method provides the accelerated predrying oftanned leatheryby the, combined action of a superheated atmosphere, which results in the sudden raise of the temperature of the skins, by conduction and convection, and in the ,applicationto said skins of infra-red radiationswith specific chemical and physical properties, Our process includes after an initial step of accelerated predrying, the step of conditioning the leather by passing it through an atmosphere of lower temperature and forced circulation of air, also at temperature higher than that of common use in the conventional methods. 7

T his invention differs from known methods in that its initialstep of accelerated predrying comprises factors of sudden temperature raise by conduction and convection to temperatures from 350 to 550 degrees Fahrenheit which are notably higher than the highest previously everused, and by the simultaneous application with this temperature raise, of infra-red radiations, for their spe-l cific chemical and physical action, relative to the wave length of said radiations, which work on the leather result-,

inglf l a deep drying, settingof the skins area, and a better distribution of the greasing materials orresidual The method herein disclosed also differs from known processes, in thatits following steps of conditioning takes place by subjecting the skins in another section of the predrying device, to an atmosphere of forced air circulation at high temperature, also higher than any usedfin theconventional methods, but lower than thatused in the prvious"step of the process. "The originality of the invention becomes apparentif in failure to obtain the desired results.

tofore used results in predrying tanned leather in a matter lblS' considered that in none of the known processesthe determining factors of the invention have been used, such as, the treatment of tanned leather by accelerated prea drying through the sudden raise in its temperature, reach ing temperatures of frorn400 to 550 degrees Fahrenheit, never used heretofore; the application of radiant energy" in the frequency of the infra-red, as specific meansof obtaining adeep predrying of the skins, ,and of resultant specific chemical and physical action,and conditioning the skins by passing them through an atmosphere of lower temperature and forced air circulation; these factors used in cpmbination and in a sequence that, if altered, results of minutes instead of hours. Also, a notable reduction in the amount of needed gumming materials is another result of the process, signifying not only a saving in the overall cost of the product, but in a better quality of the same.

1 An object of the invention is to provide a method for the accelerated predrying of tanned leather, which notably reduces the time needed for said predrying from three or more hours to from seven to fifteen minutes.

Another object of the invention is to provide a method for the accelerated predrying of tanned leather, which eifects a reduction of the amounts of gumming materials, since reducing the time of exposure of the skins to the action of the over heated air and partially predrying the skins by conduction eliminates the need for excessive gumming materials.

.Another object of the invention is to provide a. method for the accelerated predrying of tanned leather which includes the simultaneous use with the sudden raise of the skins temperature of infra-red radiations, as specific means of deep predrying of the leather, and distribution of the greasing materials, not as a by-product of the generation and use of heat.

Another object of the invention is to provide a method for the accelerated predrying of tanned leather which comprises the step of conditioning the skins by their passage in an atmosphere of circulating air, wherein the temperature has also been considerably raised. I g

A further object of the invention is to provide a process for the accelerated predrying of tanned leather which results in'a product of much better quality and appearance than those of the product resulting from known processes, said predrying process taking place in a much shorter time and at a reduced cost.

With the above and other objects in view, our invention consists in the arrangement, combination and details of construction disclosed in the drawings and specification, and then more particularly pointed out in the appended claim.

This application is a continuation in part of our copending application, Serial. Number 256,211, filed November 14, 1951, now Patent No. 2,690,069, for Method and Device for the Continuous and Accelerated Predrying of Tanned 'Leather.

In the drawing:

. Figure l is adiagrammatic plan view of a leather drying system constructed according to an embodiment of this invention.

' Figure 2 is a side elevation partly broken away showing diagrammatically interior of the heating chambers embodied in this invention.

' Referring to the drawing, the numeral, designates generally an endless monorail with which connected together pairs of leather supporting plates 11 are adapted V to be movably engaged. The plates 11 are spaced apart at their inner side, and the plates 11 may be either manually or mechanically moved along the rail 10.

A closed housing generally designated as 12 encompasses one run 13 of the rail 10 and is formed of upstanding sides 14 with hinged doors or closures 15 and 16 at'each end of the housing 12. The housing 12 is divided into a plurality of leather treating or drying chambers, one of these chambers being indicated by the numeral 17. The chamber 17 is the initial heating chamber, and in this chamber there are a series of vertically disposed combined gas burners and infra-red ray generators 18 which are positioned on opposite sides of the housing 12 below the rail 10 in a position to confront the opposite 'sides of the leather carriers 11. The carriers or plates 11, upon entering the housing 10, may be mechanically moved by means of a chain 19 which is engaged by a hook 20 carried by the lower portion of the leather carrier 11.

, The generators 18 are adapted to produce a very high temperature ranging from 350 to 550 degrees Fahrenheit 4 so as to produce on the skins a thermic shock and a sudden rise in their temperature by conduction induced by intimate contact with the supporting plates and by convection in the displacement of the overheating air masses in the chamber 17. The convection heating is controlled by forced circulation of air produced by a suction blower 21 which has the outlet side thereof connected to upper air discharge pipes 22 and 23 positioned on opposite sides of the rail 10. The intake side of the suction blower 21 is connected to lower suction or intake pipes 24 positioned in the lower portion of the housing 12 so that a relatively even heat distribution will be produced throughout the initial drying chamber 17.

The skins which are adhesively secured to the carriers 11 are also subjected to infra-red radiations in chamber 17 so as to thereby produce a deep predrying of the skins and an adequate distribution of the inherent greasing materials. The skins are positioned within the initial drying chamber 17 for a period of from two to five minutes, which time is suflicient to obtain an adequate dehydration of the skins, a setting of their area and distribution of their greasing materials. I

The second step in the drying of the skins comprises the moving of the carriers with the skins adhered thereto into a conditioning chamber 25 which communicates at.

its rear end with the forward end of chamber 17. The chamber 25 is substantially longer in length than the chamber 17 so that the skins will be subjected to a longer conditioning period and at the same time, the tempera-;

ture of the air is reduced. The reduction in the air temperature is accomplished by means of one or more suction blowers 26, which have their suction sides 27 extended into the upper forward portion of chamber 17. The blower or outlet sides of the suction blowers 26 are connected to upper discharge manifolds'or pipes 27, which extend along the length of the upper portion of conditioning chamber 25. The temperature of the air in conditioning chamber 25 will range from 200 to 300 degrees Fahrenheit.

The skins are positioned in the conditioning chamber 25 for a period of from three to seven minutes, the time of treatment in the conditioning chamber varying with the thickness of the leather treated. When the carriers, with the skins, are moved out of the forward end of housing 12, the skins may be peeled or otherwise removed from the plates forming the carriers 11 and at. this time, the skins will be in a relatively pliable condition with sufiicient moisture remaining in the skins to give the leather aproper texture.

Wth the process hereinbefore described, the product is a skin of better appearance and better quality. This process also results in a very substantial reduction in the amount of gumming materials necessary to adhere the skins to the carrier plates, and a more uniform predrying of the skins is obtained.

We do not mean to confine ourselves to the exact details of construction herein disclosed, but claim all variations falling within the purview of the appended claim.

side thereof, a series, of vertically disposed air heating elements in said first chamber, a plurality of suction fans in said second chamber for reducing the heat transmitted. in the first chamber to the hides under treatment, said.

second chamber being substantially longer than said first chamber, a forced air circulation blower communicating intake of the blower for circulating heated air through References Cited in the file of this patent UNITED STATES PATENTS Ayres Aug. 7, 1923 Andrews et a1 Nov. 1.0, 1925 Bell Nov. 1, 1932 Jennings et a1 Dec. 7, 1937 Hyde et a1 Aug. 8, 1939 Argabrite et a1. Apr. 23, 1940 Oholm June 2, 1942 Kahn et a1 Sept. 28, 1954 FOREIGN PATENTS Germany Mar. 25, 1930 

